Heat treating fluid coke briquettes



July 15, 1958 J. w. BROWN HEAT TREATING FLUID COKE BRIQUETTES Filed July27, 1955 muqzma} 1% Em; l F vw w: Iv mm m Iv Iv mzow uztfiz mzow MXOO0541 James W. Brown Inventor By X C'Wflomey r 2,843,462 lQe PatentedJuly 15, 1958 HEAT TREATING FLUID COKE BRIQUETIES James W. Brown,Mountainside, N. 1., assignor to Esso Research and Engineering Company,a corporation of Delaware Application July 27, 1955, Serial No. 524,747

3 Claims. (Cl. 44-24) This invention relates to improvements in the heathardening of fluid coke briquettes. More particularly it relates to aprocess of this nature wherein the briquettes are heat hardened bytreating them countercurrently with upflowing inert gases. The bindermaterials are cracked and the tar condensate is utilized as additionalbinder.

There has recently been developed an improved process known as the fluidcoking process for the production of fluid coke and the thermalconversion of heavy hydrocarbon oils to lighter fractions, e. g. seePatent No. 2,725,349, granted November 29, 1955, and Patent No.2,721,169, granted October 18, 1955. For completeness the process isdescribed in further detail below although it should be understood thatthe fluid coking process itself is no part of this invention.

The fluid coking unit consists basically of a reaction vessel or cokerand a heater or burner vessel. In a typical operation the heavy oil tobe processed is injected into the reaction vessel containing a dense,turbulent fluidized bed of hot inert solid particles, preferably cokeparticles. A transfer line or staged reactors can be employed. Uniformtemperature exists in the coking bed. Uniform mixing in the bed resultsin virtually isothermal conditions and effects instantaneousdistribution of the feed stock. In the reaction zone the feed stock ispartially vaporized and partially cracked. Effluent vapors are removedfrom the coking vessel and sent to a fractionator for the recovery ofgas and light distillates therefrom. Any heavy bottoms is usuallyreturned to the coking vessel. The coke produced in the process remainsin the bed coated on the solid particles. Stripping steam is injectedinto the stripper to remove oil from the coke particles prior to thepassage of the coke to the burner.

The heat for carrying out the endothermic coking reaction is generatedin the burner vessel, usually but not necessarily separate. A stream ofcoke is thus transferred from the reactor to the burner vessel, such asa transfer line or fluid bed burner, employing a standpipe and risersystem; air being supplied to the riser for conveying the solids to theburner. Sufficient coke or added carbonaceous matter is burned in theburning vessel to bring the solids therein up to a temperaturesuflicient to maintain the system in heat balance. The burner solids aremaintained at a higher temperature than the solids in the reactor. About5% of coke, based on the feed, is burned for this purpose. This mayamount to approximately 15 to 30 wt. percent of the coke made in theprocess. The net coke production, Which represents the coke make lessthe coke burned, is Withdrawn.

Heavy hydrocarbon oil feeds suitable for the coking process includeheavy crudes, atmospheric and crude vacuum bottoms, pitch asphalt, otherheavy hydrocarbon petroleum residua or mixtures thereof. Typically suchfeeds can have an initial boiling point of about 700 F. or higher, an A.P. I. gravity of about to 20, and a Conradson carbon residue content ofabout to 40 wt. percent. (As to Conradson carbon residue see A. S. T. M.test D-189-41.)

A problem in the marketing of the fluid coke product is the small sizeof the particles, predominantly, i. e. about 6090 wt. percent in therange of 20 to mesh. The production of substantially larger particles isinconsistent with satisfactory operation of the fluid bed. On the otherhand industrial requirements for coke often necessitate particles havinga diameter of about at least inch to 1 inch.

These fluid coke particles have accordingly been compacted intobriquettes using various carbonaceous binder substances. Theagglutinating carbonaceous binder substances that can be utilizedinclude suitable hydrocarbon binders, such as asphalt and other heavypetroleum residues, aromatic tars, e. g. vacuum reduced thermal tars,heavy ends of coal tar, such as coal tar pitches having a minimumsoftening point of about C., and heavy ends from the coking operation,i. e., 1000 F. scrubber bottoms. Some specific trade examples of thebinders are Elk Basin vacuum residum F. softening point), Enjay 160Asphalt and Hawkins coker bottoms. These substances are utilized in anamount of about 5 to 25 wt. percent based on the coke charge andpreferably 8 to 15 wt. percent.

This invention is especially suited to utilization of lowvalue petroleumresidues which are inferior binders unless specially treated. Normally,when a petroleum residue is decomposed by heating, the carbonaceousresidue is less than from a more aromatic binder such as from coal tar.It has now been found, however, that the conditions desirable for theheat hardening of fluid coke agglomerates are also the conditions bestsuited to converting a petroleum residue into a good binder with highcokeforming potentialities. The most important condition is a slow rateof heating. A binder so treated has less tendency to soften duringsubsequent heating and is also more susceptible to additionaltreatments, to be described later, which reduce its tendency to softenduring heating.

The important advantage of using a petroleum residue is the low costrelative to other available binders. For example, when 10% binder isused in agglomeration the cost saving would be in the range of $1.00 to$3.00 per ton of coke agglomerated.

The fluid coke can be used as is to make briquettes, but the behavior ofbriquettes during heating and the strength of the final products areimproved by grinding part or all of the coke to produce finer particles..This mixture with binder is then 'briquetted by molding in a hydraulicpress at a pressure of about 2,000 to 20,000 p. s. i. Pressures of 2000to 6000 p. s. i. are usually adequate. Roll presses such as thosecommonly employed to make briquettes from coal and other materials canbe used. Such machines are described in the Chemical Engineering articleAgglomeration, October 1951. The mixtures pass directly to the pressingrolls.

These briquettes require heat hardening at temperatures of above 700 F.to decompose the binder to a carbonaceous residue and to produceadequate strength and cohesion. Heating up to 16002000 F. is usuallydesirable to devolatilize the coke. F. range, however, because of themelting of the binder material results in the deformation of thecompactions and also adherence to each other. In addition elevated.

temperatures tend to destroy the binder by preferential Heating in the200 700".

ening the briquettes'by countercurrently contacting them with hot inertgases. The briquettes are thus heat hardened without deformation oroxidation. The binder materials are cracked. A tar fraction is condensedand this condensate is then used as a superior additional binder for thebriquetting operation. Further details follow.

Part of the fluid coke is ground so as to pass through a 100 meshscreen. The amount of grinding to be done depends on the desiredstrength of the agglomerates as well as on the quality of the binderwith which it is to be mixed. High viscosity binders are especiallydifficult to mix with fine coke. The fluid coke is admixed with thebinder material at a temperature in the range of 200 to 400 F.

The mixture is then molded under pressure as also explained above but ata lower temperature than the mixing step, i. e., 150 to 250 F. Theresultant briquettes are then sent to a heating zone, e. g., a shaftfurnace, where they are heated to a temperature in the range of 1200 to2000 F., preferably 1600 to 2000 F. by countercurrent contacting withhot inert gases which enter the furnace at a temperature in the range of2000 to 3000 F. The rate of heating the agglomerates is 2 to 15 F./min.depending on binder quality and agglomerate strength. The heating timeis in the range of 1 to 10 hours. The hot inert gases include materialslike CO CO, N etc. Preferably the inert gases are flue gases fromcombustion systems. The combustible material can be fluid coke itself oran extraneous fuel such as fuel oil or natural gas. The combustion issupported by an oxygen containing gas such as air but the combustionshould take place with a deficiency of oxygen so as to assure theabsence of oxygen in the furnace.

The inert gases as well as evolved cracked binder vapors are thenremoved from the heat treating zone and cooled. The conditions arecontrolled such as to condense a fraction having a minimum boiling pointin the range of 400 to 700 F. This is most conveniently accomplished byintroduction of a quench medium which may be water, steam or condensed,cooled hydrocarbons. The temperature of the quench can be adjusted so asto condense the desired hydrocarbons without condensing water whichwould form emulsions. Subsequent cooling to a convenient temperaturearound 80 to 100 F. removes much of the water vapor and lighthydrocarbons. The condensate is highly aromatic, lower boiling and lessviscous than the binder material used originally. In general, the poorerthe original binder, the more cracked binder will be recovered for usein the condensation step. The condensate would normally have a boilingrange from about 500 F. to well over 1000 F.

At the temperature of mixing with the coke around 200 to 400 F., therecycle binder has a viscosity of 40 to 200 Saybolt Seconds Furol. Itsgravity is usually less than A. P. I. and displays a high coke-formingtendency when heated. This condensate is then recycled to the mixingoperation to facilitate the latter and conveniently the inert gasesafter reheating are returned to the heat treating operation.

The recycle condensate thus utilized is in the range of 2 to 10 wt.percent based on the fluid coke charged to the briquetting operation.

This invention will be better understood by reference to the followingexample and description in connection with the flow diagram shown in thedrawing.

Referring now to the flow diagram, fluid coke is fed through line 1 intomixing zone 15 wherein it is admixed with 10 wt. percent scrubberbottoms from fiuid coking of heavy Elk Basin vacuum pitch from line 2 ata temperature of 250 F. The resultant mixture together with wt. percentof the recycle binder from line 14 passes through line 3 intobriquetting zone 4 where it is molded at a temperature of 150 F. and apressure of 4000 p. s. i. The resultant briquettes leave by way of line5 and are slowly passed downward as a moving bed through .4. shaftfurnace heating zone 6. The briquettes are countercurrently contactedwith upflowing flue gas from auxiliary furnace 11 and line 12 and arethus hardened by slowly heating to 1800 F. at an average rate of 5 F.per minute. The heat hardened briquettes are cooled before removal byintroducing wet steam through line 17. Finished briquettes may also becooled by introducing water or recycle gas into line 17. The cooled,heat hardened briquettes are withdrawn from line 13 by a feedingmechanism 18.

The binder undergoes cracking at the heat hardening temperature andcracked binder vapors along with flue gases are removed overhead throughline 7. Quench material such as water or recycled binder is introducedthrough line 16 so as to condense a condensate having a minimum boilingpoint of 500 F. No difl'iculty is encountered in quenching provided ittakes place quickly and provided the temperature is above that at whichwater condenses. A venturi-type quench is the preferred apparatus. Inseparation zone 8 the uncondensed vapor is separated from thecondensate. The latter is recycled through line 14 to mixing zone 15. 5wt. percent binder based on the fluid coke charge is recycled in thismanner.

The flue gases are then quenched in venturi-scrubber 19 to removeremaining condensable hydrocarbons which are collected in separator 20.Flue gases are then vented through line 9 or recirculated by line 10,compressor 21, furnace 11 and line 12 back to heating zone 6.

The conditions usually encountered in a fluid coker for fuels are alsolisted below so as to further illustrate how the fluid coke wasprepared.

Conditions in fluid coker reactor The advantages of this invention areapparent to the skilled in the art. A distinct saving in expensivebinder material is provided. Improved mixing of binder and fluid coke isobtained. This improves the strength of the agglomerate. Briquettes areheat hardened Without deformation or surface disintegration.

The reduction in deformation tendency is partly attributable to theimproved mixing and partly to the better properties of the recyclebinder. Furthermore, the cracked binder is especially susceptible toadditional treatments to fuither decrease the amount of deformationencountered. Such treatments include air blowing, treatment withchemicals such as sulfuric acid or thermal pretreating such as a shortheating on a moving belt prior to introduction into the shaft furnace.In the case of thermal pretreatment the recycle binder tends to set intoa hard form because of its unsaturated chemical nature.

The coke agglomerates produced by use of the recycle binder have a moreporous structure than those produced from binders which display asmaller amount of thermal cracking. The porous structure makes this cokeespecially reactive in metallurgical use.

The process of this invention also has utility in preparing othercompactions such as pellets and extrusions and from other fine solidsbesides fluid coke.

It is to be understood that this invention is not limited to thespecific examples which have been offered merely as illustrations andthat modifications may be made without departing from the spirit of theinvention.

What is claimed is:

1. A process for preparing stable briquettes from fluid coke particleswhich comprises the steps of admixing the particles with anagglutinating carbonaceous binder at a temperature in the range of 200to 400 F.; molding the resulting mixture into briquettes at a lowertemperature, one in the range of 150 to 250 F. and a pressure in therange of 2000 to 20,000 p. s. i.; heat hardening the briquettes at atemperature in the range of 1200 to 2000 F. in a heating zone at aheating rate of 2 to 15 F. 1 min. by countercurrently contacting themwith upflowing inert gases at a temperature in the range of 2000 to 3000F., the total heating time being in the range of 1 to 10 hours;withdrawing evolved, cracked binder vapors along with inert gases fromthe heating zone; cooling the vapors so as to obtain a condensate havinga minimum boiling point in the range of 400 to 700 F., the boiling pointand viscosity of the condensate being less than that of theagglutinating carbonaceous binder; recycling this condensate asadditional binder to the admixing step and withdrawing stable briquettesfrom the heating zone, the total amount of binder utilized being in therange of 5 to 25 wt. percent based on the fluid coke particles of whichthe condensate represents 2 to 10 wt. percent based on the cokeparticles.

References Cited in the file of this patent UNITED STATES PATENTS1,667,358 Robeson Apr. 24, 1928 1,972,944 Morrell Sept. 11, 19342,556,154 Kern June 5, 1951 2,709,676 Krebs May 31, 1955 2,776,935Jahnig et a1. Jan. 8, 1957 OTHER REFERENCES Residual Oils Fluid Coked toEliminate Heavy Fuel Problem, Voorhees and Martin, Proceedings of A. P.I., 1953, see. III, pages 39-46.

Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No, 2,843,462 July 15, 1958 James Wo Brown It is hereby certifiedthat error appears in the printed specification of the above numberedpatent requiring correction and that the said Letters Patent should readas corrected below.

0 o Column 5, line 6, for "15 .F(, 'l mine" read 15 Fa/mino Signed andsealed this 28th day of October 19580,

ttest:

KARL AXLINE ROBERT c. WATSON Commissioner of Patents

1. A PROCESS FOR PREPARING STABLE BRIQUETTES FROM FLUID COKE PARTICLESWHICH COMPRISES THE STEPS OF ADMIXING THE PARTICLES WITH ANAGGLUTINATING CARBONACEOUS BINDER AT A TEMPERATURE IN THE RANGE OF 200*TO 400*F., MOLDING THE RESULTING MIXTURE INTO BRIQUETTES AT A LOWERTEMPERATURE, ONE IN THE RANGE OF 150* TO 250*F. AND A PRESSURE IN THERANGE OF 2000 TO 20,000 P. S. I.; HEAT HARDENING THE BRIQUETTES AT ATEMPERATURE IN THE RANGE OF 1200* TO 2000*F. IN A HEATING ZONE AT AHEATING RATE OF 2* TO 15*F. 1 MIN. BY COUNTERCURRENTLY CONTACTING THEMWITH UPFLOWING INERT GASES AT A TEMPERATURE IN THE RANGE OF 2000* TO3000*F. THE TOTAL HEATING TIME BEING IN THE RANGE OF 1 TO 10 HOURS;WITHDRAWING EVOLVED, CRACKED BINDER VAPORS ALONG WITH INERT GASES FROMTHE HEATING ZONE; COOLING THE VAPORS SO AS TO OBTAIN A CONDENSATE HAVINGA MINIMUM BOILING POINT IN THE RANGE OF 400* TO 700*F., THE BOILINGPOINT AND VISCOSITY OF THE CONDENSATE BEING LESS THAN THAT OF THEAGGLUTIATING CARBONACEOUS BINDER; RECYCLING THIS CONDENSATE ASADDITIONAL BINDER TO THE ADMIXING STEP AND WITHDRAWING STABLE BRIQUETTESFROM THE HEATING ZONE, THE TOTAL AMOUNT OF BINDER UTILIZED BEING IN THERANGE OF 5 TO 25 WT. PERCENT BASED ON THE FLUID COKE PARTICLES OF WHICHTHE CONDENSATE REPRESENTS 2 TO 10 WT. PERCENT BASED ON THE COKEPARTICLES.